1. Field of the Invention
The invention relates to a method for preventing work pieces of iron or iron alloys, the surfaces of which touch each other at elevated temperature or simultaneously under mechanical pressure, from sticking together.
2. Background of the Invention
In inductive heating facilities for forgings, the material to be heated in the form of lined-up blocks of iron or iron alloys is pushed through the induction coil and is thereby heated to the forging temperature. In many cases, the individual blocks stick together at the touching end faces, which leads to disturbances in the operation.
The cause of this sticking-together is sintering of the metallic block ends which are pushed together. This sintering process is aided by the heating of the blocks to the forging temperature, by the contact pressure in pushing the blocks through the induction coil, and by the residence time of the blocks in the induction coil during which the temperature and the pressure are active. The atmosphere also has a substantial influence on the sintering process. At certain oxygen potentials and temperatures, oxygen is adsorbed on the iron surface in a chemisorption layer, which additionally activates the sintering process. The temperatures occurring in the heating device are of an order of magnitude which induces this activated sintering.
According to the present state of the art, the sintering-together of the metallic block ends is prevented by the application of a paste of high-melting, ceramic base materials, especially aluminum oxide, which spaces the metal surfaces of two adjacent forging blocks at high heating temperatures a sufficient distance, so that the sintering process mentioned above does not take place. A disadvantage of this method is that the ceramic components of such a paste, even if they are present in the most finely-divided form, lead to contamination at the forging and, over the long term, cause damage to the forging tool.